CVE-2015-6366: Cisco IOS 15.2(04)M6 and 15.4(03)S lets physical-interface ACLs supersede tunnel-interface ACLs, which allo...

Security readout for executives and security teams

This Cisco IOS flaw can let traffic carried through tunnels bypass restrictions that administrators intended to enforce on tunnel interfaces. The issue is narrow but important for routers relying on tunnel ACLs for segmentation or filtering. The provided sources do not include a CVSS score or patch details. Exposure is most likely on Cisco IOS devices running the named versions and using tunnel interfaces with ACLs as a security boundary. Environments without tunnels, without tunnel-interface ACL dependencies, or not running the named versions are less likely exposed based on the supplied evidence. Treat this as a targeted network-control bypass risk. It is not proven actively exploited in the provided sources, but affected routers may silently allow traffic that policy intended to block. Prioritize internet-facing, partner, and sensitive-network tunnel paths. Mitigation focus: Identify Cisco IOS devices running 15.2(04)M6 or 15.4(03)S.; Review Cisco advisory cisco-sa-20151112-ios2 for fixed releases or vendor workarounds.; Avoid relying solely on tunnel-interface ACLs on affected versions..

Prepared

Jun 13, 2026, 21:45 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.